Throttle control fault detection and tolerance method/system

ABSTRACT

A fault sensing and tolerant logic (FIG. 6) is provided for a control system/method for an automated mechanical transmission system (12) including a throttle dip override device (34).

BACKGROUND OF THE INVENTION

1. Related Applications

This application is related to co-pending U.S. patent applications:

Ser. No. 07/698,751 entitled COMPOUND POWER DOWNSHIFT METHOD/SYSTEM;

Ser. No. 07/698,745 entitled RANGE SHIFTING ONLY FAULT TOLERANCEMETHOD/SYSTEM;

Ser. No. 07/697,384 entitled TOOTH BUTT/BUZZ CONTROL METHOD/SYSTEM;,

Ser. No. 07/698,752 entitled SMOOTH UPSHIFT CONTROL METHOD/SYSTEM;

Ser. No. 07/698,017 entitled DRIVELINE TORQUE LIMIT CONTROLSTRATEGY-USING SAE J1922 TYPE ENGINE CONTROL;

Ser. No. 07/697,814 entitled TORQUE CONVERTER SLIP RATE BASED SKIP POWERDOWNSHIFT CONTROL STRATEGY, all filed the same day, May 9, 1991, andassigned to the same assignee, Eaton Corporation, as this application.

2. Field of the Invention

The present invention relates to a control system and control method forcontrolling the operation of an automated mechanical transmissionsystem, preferably of the type including a fuel throttle devicecontrolled engine, a torque converter, a lock-up/disconnect clutchassembly and a mechanical transmission.

In particular, the present invention relates to a fault tolerancecontrol system/method for an automated transmission system as describedabove wherein the fuel throttling device is a throttle dip overridedevice effective to reduce or shut off fuel to the engine to apredetermined relatively low value (at or below idle fuel) regardless ofthe operators setting of the accelerator pedal and, more particularly,relates to a fault sensing and tolerance control system/method for suchan automated transmission system.

3. Description of the Prior Art

Mechanical transmission systems of the compound range, splitter orcombined range and splitter type are well known in the prior art as maybe seen by reference to U.S. Pat. Nos. 4,788,889; 4,754,665 and4,735,109, the disclosures of which are incorporated by reference.

Automatic mechanical transmission systems comprising mechanicaltransmissions and controls and actuators to at least partiallyautomatically shift same, usually electronically controlled inaccordance with sensed inputs and predetermined logic rules, are known.Examples of such systems may be seen by reference to U.S. Pat. Nos.4,648,290; 4,595,986; 4,527,447; 4,361,060; 4,140,031 and 4,081,065, thedisclosures of which hereby incorporated by reference. Such systems mayalso be seen by reference to SAE Paper No. 831776 titled "AUTOMATEDMECHANICAL TRANSMISSION CONTROLS", the disclosure of which is herebyincorporated by reference.

Fault tolerance logic routines for automatic transmissions are known asmay be seen by reference to U S. Pat. Nos. 4,922,425; 4,849,899 and4,899,279, the disclosures of which are hereby incorporated byreference.

Automatic transmission systems including a torque converter drivinglyinterposed a drive engine and a mechanical change gear transmissionand/or including torque converter bypass or lock-up devices are alsoknown as may be seen by reference to U.S. Pat. Nos. 3,593,596;4,261,216; 4,271,724; 4,351,205 and 4,375,171, the disclosures of whichare hereby incorporated by reference.

Automatic mechanical transmission systems utilizing power synchronizerdevices, i.e. devices independent of engine speed to provide input shaftbraking and acceleration, and not manipulation of engine speed, tosynchronize the transmission jaw clutch members are known in the priorart. Examples of such systems may be seen by reference to U.S. Pat. Nos.3,478,851, 4,023,443; 4,140,031 and 4,614,126, the disclosures of whichare hereby incorporated by reference.

Automatic mechanical transmission systems having a power synchronizerand also having a torque converter drivingly interposed a drive engineand the transmission input shaft, and including a torque converterlock-up/disconnect clutch assembly, are known. Examples of such systemsmay be seen by reference to U.S. Pat. Nos. 4,784,019 and 4,860,861 andS.A.E. Paper No. 881830 entitled "THE EATON CEEMAT (CONVERTER ENHANCEDELECTRONICALLY MANAGED AUTOMATIC TRANSMISSION)", the disclosures ofwhich are hereby incorporated by reference.

Such transmission systems provide an automatic mechanical transmissionsystem utilizing a mechanical change gear transmission of a structureidentical or substantially identical to the structure of transmissionsintended for manual usage, providing the advantages of a torqueconverter for vehicle start-ups and the advantages of nonslippingconnection between the engine and transmission at higher vehiclespeeds/gear ratios and providing relatively rapid synchronization of thetransmission positive jaw clutches. By providing an automatic mechanicaltransmission system based upon the same, or substantially the same,mechanical change gear transmission utilized for manual transmissionsystems, manufacturing, inventory and maintenance cost savings areobtained. To the transmission is added, if necessary, shiftingmechanisms suitable for automatic control by solenoids or the like. Anexample of such a shifting mechanism may be seen by reference toabove-mentioned U.S. Pat. Nos. 4,361,060 and 4,899,607 and U.S. Pat.Nos. 4,873,881; 4,722,237 and 4,445,393, the disclosures of which arehereby incorporated by reference. A power synchronizer mechanism asdisclosed in above-mentioned U.S. Pat. Nos. 4,614,126; 3,478,851 or4,023,443 is also added for synchronizing the transmission positive jawclutches.

A torque converter is drivingly interposed the drive engine andtransmission. A torque converter lock-up and disconnect clutch structureis provided comprising a first and a second separate, independentlyoperable, clutches, preferably friction clutches, for coupling thetorque converter driven member or turbine to the transmission inputshaft and for coupling the torque converter input or impeller (i.e. theengine output) to the transmission input shaft, respectively.

The torque converter is drivingly interconnected between the engine andtransmission only when the first coupling is engaged and the seconddisengaged. The torque converter is locked-up, i.e. the turbine drivendirectly by the engine, when the second clutch is engaged. Thetransmission is driven directly from the engine, whenever the secondclutch is engaged simultaneously with the first clutch.

When the first coupling is disengaged, regardless of the condition ofthe second coupling, the transmission input shaft is disconnected fromthe engine torque and also from the inertia of the torque converter andfrom the inertia of the second coupling allowing the jaw clutches to beeasily disengaged, the power synchronizer mechanism to act quickly dueto relatively low inertia on the input shaft and also allowing aselected gear to be pre-engaged with the vehicle at rest and in thedrive condition.

With automated transmission systems of the type described, it isimportant to have a method or system for sensing a faulty throttle dipoverride device and for adapting fault tolerance operation logic if sucha fault is sensed.

SUMMARY OF THE INVENTION

In accordance with the present invention, the drawbacks of the prior artare overcome or minimized by the provision, in an automated mechanicaltransmission system of the type described having a throttle dip overridedevice, of a control method/system for sensing a faulty throttle dipoverride device and for adapting a fault tolerant mode of operation inresponse to sensing such a fault.

The above is accomplished, preferably in an automatic mechanicaltransmission system based upon a mechanical change gear transmission towhich is added shifting mechanisms suitable for automatic control,preferably, a power synchronizer mechanism as disclosed inabove-mentioned U.S. Pat. No. 4,614,126, preferably a torque converterdrivingly interposed the drive engine and transmission and a torqueconverter lock-up and disconnect clutch structure comprising a first anda second separate, independently operable, clutches, preferably frictionclutches, for coupling the torque converter driven member or turbine tothe transmission input shaft and for coupling the torque converter inputor impeller (i.e. the engine output) to the transmission input shaft,respectively, and a throttle dip override device for selectivelyreducing fuel to the engine to a selected relatively low valueregardless of operator's setting of the throttle pedal by the provisionof control logic which will sense engine speed before and after thethrottle dip is actuated to determine if the throttle dip is operating,and, if a fault is sensed, which will prohibit upshifts until theoperator reduces accelerator pedal setting to below a predeterminedreference value.

Accordingly, it is an object of the present invention to provide a newand improved automatic mechanical transmission system.

Another object of the present invention is to provide an automatedmechanical transmission system having a throttle dip override device,and preferably a power synchronizer, which includes logic for sensingand tolerating failure to actuate type faults in the throttle dipoverride device.

These and other objects and advantages of the present invention willbecome apparent from a reading of the description of the preferredembodiment taken with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of the torque converter and torque converterdisconnect and bypass clutch structure of the present invention.

FIG. 2 is a schematic illustration of the automatic mechanicaltransmission system of the present invention.

FIG. 3 is a partial view, in section, of the automatic mechanicaltransmission system of the present invention.

FIG. 4 is a graphical representation of a typical shift sequence for thetransmission of FIG. 2.

FIG. 5 is a symbolic representation of the shift pattern for thetransmission of FIG. 3.

FIG. 6 is a symbolic representation, in flow chart format, of the faultsensing and tolerance logic of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Certain terminology will be used in the following description forconvenience and reference only and will not be limiting. The words"upwardly", "downwardly", "rightwardly" and "leftwardly" will designatedirections in the drawings to which reference is made. The words"inwardly", and "outwardly", refer to directions towards and away from,respectively, the geometric center of the device and designated partsthereof. The above applies to the words above specifically mentioned,derivatives thereof and words of similar import.

The torque converter lock-up and disconnect clutch assembly 10 and anautomatic mechanical transmission system 12 utilizing same, of thepresent invention, are schematically illustrated in FIGS. 1, 2 and 3.The term "automatic mechanical transmission system" as used herein,shall mean a system comprising at least a throttle device controlledheat engine 16, a multi-speed jaw clutch type change gear transmission14, a nonpositive coupling device such as a master friction clutchand/or a fluid coupling 10/20 interposed the engine and the transmissionand a control unit 50 for automatically controlling same. Such systemswill, of course, also include sensors and/or actuators for sending inputsignals to and/or receiving command output signals from the controlunit.

While the present invention is particularly well suited for use inconnection with transmission systems having a torque converter andtorque converter lockup/disconnect clutch, the invention is alsoapplicable to transmission systems having a standard friction masterclutch drivingly interposed the engine and the transmission.

The automatic mechanical transmission system 12 of the present inventionis intended for use on a land vehicle, such as a heavy duty truck, butis not limited to such use. The automatic mechanical transmission system12 illustrated includes an automatic multi-speed mechanical change geartransmission 14 driven by a prime mover throttle device controlledengine 16 (such as a diesel engine) through a fluid coupling or torqueconverter assembly 20. The output of the automatic transmission 14 is anoutput shaft 22 which is adapted for driving connection to anappropriate vehicle component such as the differential of a drive axle,a transfer case, or the like as is well known in the prior art.

As will be discussed in greater detail below, the torque converterlock-up and disconnect clutch assembly 10 includes two separate,independently engageable clutches, preferably friction clutches, atorque converter disconnect clutch 24 and a torque converter lock-up orbypass clutch 26. The transmission 14 includes a transmission operatingmechanism 28 which is preferably in the format of a pressurized fluidactuated shifting assembly of the type disclosed in above-mentioned U.S.Pat. No. 4,445,393. The transmission also preferably includes a powersynchronizer assembly 30 which may be of the type illustrated anddisclosed in above-mentioned U.S. Pat. Nos. 3,478,851, 4,023,443 or4,614,126.

The present invention is also applicable to automated mechanicaltransmission systems not including a power synchronizer assembly.

The above-mentioned power train components are acted upon and monitoredby several devices, each of which are known in the prior art and will bediscussed in greater detail below. These devices may include a throttleposition monitor assembly 32, which senses the position of the operatorcontrolled vehicle throttle pedal or other fuel throttling device, athrottle control 34 which controls the supply of fuel to the engine, anengine speed sensor assembly 36 which senses the rotational speed of theengine, a torque converter disconnect clutch and lock-up clutch operator40 which operates the torque converter disconnect and lock-up clutches,a transmission input shaft speed sensor 42, a transmission output shaftspeed sensor 44, a transmission shifting mechanism operator 46 forcontrolling the operation of transmission shifting mechanism 28 and/or apower synchronizer mechanism actuator 48 for controlling the operationof power synchronizer mechanism 30.

The throttle control 34 may simply be an override device to reduce("dip") fuel to the engine to a set or variable level regardless of theoperator's positioning of the throttle pedal.

Typically, the override device is a solenoid controlled device which,when actuated, will reduce fuel to the engine to a relatively low valuesuch as the amount of fuel required to retain engine speed at or belowidle speed. In such systems, the engine fueling device, such as aninjector rack or the like, may be directly controlled by the vehicleaccelerator pedal subject to being overridden by the throttle dipoverride device or may be controlled by a controller receiving inputsfrom the accelerator pedal.

The above-mentioned devices supply information to and/or accept commandsfrom an electronic central processing unit (ECU) 50. The centralprocessing unit or controller 50 is preferably based on a digitalmicroprocessor, the specific configuration and structure of which formno part of the present invention. The central processing unit 50 alsoreceives information from a shift control or mode selector assembly 52by which the operator may select a reverse (R), a neutral (N) or severalforward drive (D, D_(L)) modes of operation of the vehicle. Typically,the D mode of operation is for on-highway vehicle travel while the D_(L)mode of operation is for off-road operation.

Typically, the system also includes various sensors, circuits and/orlogic routines for sensing and reacting to sensor and/or actuatorfailures.

As is known, the central processing unit 50 receives inputs from thevarious sensors and/or operating devices. In addition to these directinputs, the central processing unit 50 may be provided with circuitryand/or logic for differentiating the input signals to provide calculatedsignals indicative of the rate of change of the various monitoreddevices, means to compare the input signals and/or memory means forstoring certain input information, such as the direction of the lastshift, and means for clearing the memory upon occurrence ofpredetermined events. Specific circuitry for providing theabove-mentioned functions is known in the prior art and an examplethereof may be seen by reference to above-mentioned U.S. Pat. Nos.4,361,060 and 4,595,986 and/or by reference to a technical paperentitled "THE AUTOMATION OF MECHANICAL TRANSMISSIONS" publishedproceedings of a joint IEEE/SAE conference entitled InternationalCongress 20 on Transportation Electronics, IEEE Catalog Number84CH1988-5, the disclosure of which is hereby incorporated by reference.

As is well known in the operation/function of electronic control units,especially microprocessor based ECUs, the various logic functions can beperformed by discrete hardwired logic units or by a single logic unitoperating under different portions or subroutines of the control systemlogic rules (i.e. the software).

A more detailed schematic illustration of the torque converter 20 andtorque converter lock-up and disconnect clutch assembly 10 drivinglyinterposed engine 16 and automatic change gear transmission 14 may beseen by reference to FIG. 1. The torque converter assembly 20 isconventional in that it includes a fluid coupling of the torqueconverter type having an impeller 54 driven by the engine output orcrank shaft 56 through a shroud 58, a turbine 60 hydraulically driven bythe impeller and a stator or runner 62 which becomes grounded to ahousing 64 via a one-way roller clutch 66 carried by a shaft 68 groundedto the housing 64. Shroud 58 also drives a pump 70 for pressurizing thetorque converter, lubricating the transmission, selectively pressuringthe transmission shifting mechanism 28 and/or power synchronizingmechanism 30 and/or operating the disconnect and bypass clutches 24 and26. Pump 70 may be of any known structure such as, for example, a wellknown crescent gear pump.

The transmission 14 includes an input shaft 72 driven by the engine 16via the torque converter assembly 20 and/or lock-up and disconnectclutch assembly 10. Transmission input shaft 72 carries a connectingmember 74 fixed thereto for rotation therewith. Connecting member 74includes a portion 76 associated with the torque converter disconnectclutch 24 and a second hub portion 78 splined for association with theinput shaft. Briefly, as will be described in greater detail below,torque converter disconnect clutch 24 may be engaged or disengaged,independently of engagement or disengagement of lock-up clutch 26, tofrictionally engage or disengage a connecting member 79 which isassociated with the torque converter turbine 60 and a member of thelock-up clutch 26, to and from the transmission input shaft 72 viaportion 76 of connecting member 74. Torque converter lock-up clutch 26may be frictionally engaged or disengaged, independent of the engagementor disengagement of disconnect clutch 24, to frictionally engage theengine crankshaft 56, and shroud 58 driven thereby, to the connectingmember 79.

Engagement of torque converter lock-up clutch 26 will engage the enginecrankshaft 56, via shroud 58, directly with the connecting member 79,regardless of the engaged or disengaged condition of torque converterdisconnect clutch 24, and thus provides an effective lock-up forlocking-up the torque converter 20 and driving transmission 14 directlyfrom the engine 16 if disconnect clutch 24 is engaged. Additionally, atspeeds above torque converter lock-up speed, the lock-up clutch 26 neednot be engaged and disengaged during shifting as disengagement of clutch24 disconnects the inertia of connection member 79 from input shaft 72.

If the torque converter bypass clutch or lock-up 26 is disconnected, andthe torque converter disconnect clutch 24 is engaged, the transmission14 will be driven from engine 16 via the torque converter fluid couplingas is well known in the prior art. If the torque converter disconnectclutch 24 is disengaged, regardless of the condition of lock-up clutch26, the transmission input shaft 72 is drivingly disengaged from anydrive torque supplied by the engine or any inertial drag supplied by thetorque converter, the engine and clutch 26. Disconnecting of thetransmission input shaft 72 from the inertial affects of the engine,clutch 26 and/or torque converter allows the rotational speed of theinput shaft 72, and all transmission gearing drivingly connectedthereto, to be accelerated or decelerated by the transmission powersynchronizer mechanism 30 in a more rapid manner for purposes of morerapidly achieving synchronization during a downshift or upshift of thetransmission and also allows the power synchronizer 30 to cause theinput shaft 72 to rotate at a rotational speed greater than any governedengine speed.

When the vehicle is at rest with the mode selector in the drive oroff-highway drive mode, the disconnect clutch 24 will be engaged and thelock-up clutch 26 disengaged allowing for torque converter start-up withits well known advantages. At above a given vehicle speed and/or gearratio, the advantages of torque converter operation are no longerrequired, and the increased efficiency of a direct drive between thedrive engine and transmission is required. Upon these conditions, thetorque converter lock-up clutch 26 will be maintained engaged allowingthe transmission input shaft 72 to be driven directly from the enginevia the torque converter shroud 58 and connecting member 79 when thedisconnect clutch 24 is engaged.

As discussed above, clutch 24 will be disengaged to shift from apreviously engaged gear to neutral, to allow the power synchronizer 30to synchronize the jaw clutch members of the gear to be engaged and toallow engagement of the synchronized jaw clutches of the gear to beengaged.

Selection of the desired gear ratio and selection of the requiredengaged or disengaged condition of the torque converter disconnect orlock-up clutches, as well as the issuance of command signals to thevarious clutch and transmission operators is accomplished by the centralprocessing unit 50 in a manner which is known in the prior art and whichmay be appreciated in greater detail by reference to above-mentionedU.S. Pat. Nos. 4,361,060 and 4,595,986.

The compound transmission 14 is illustrated in in greater detail in FIG.3 and is of the type wherein the main section countershaft orcountershafts 90 are coaxially aligned with the auxiliary sectioncountershaft or countershafts 92. Transmission 14 is of a relativelystandard design and is preferably of the twin countershaft type only oneof which countershafts in the main and auxiliary sections, 94 and 96,respectively, is shown. Examples of such transmissions having coaxiallyaligned main section and auxiliary section countershafts may be seen byreference to U.S. Pat. Nos. 3,105,395 and 3,138,965, the disclosures ofwhich are incorporated by reference.

Transmission 14 includes input shaft 72 to which member 78 is fixed forrotation therewith and which additionally carries input gear 98nonrotatably attached thereto. Main section countershaft 90 issubstantially parallel to mainshaft 100 and is provided withcountershaft gears 102, 104, 106, 108, 110 and 112 fixed for rotationtherewith. A plurality of mainshaft gears, also called ratio gears, 114,116, 118 and 120, surround the mainshaft and are selectively clutchablethereto, one at a time, by double sided positive jaw clutch collars 122,124 and 126. Jaw clutch collar 122 may also clutch the input shaft 72directly to the mainshaft 100 while clutch collar 126 may clutch reversemainshaft gear 128 to the mainshaft.

The mainshaft gears 114, 116, 118 and 120 circle the mainshaft and arein continuous meshing engagement with, and are preferably supported by,opposed pairs of countershaft gears 104, 106, 108 and 110 which mountingmeans and the special advantages resulting therefrom are explained ingreater detail in above-mentioned U.S. Pat. Nos. 3,105,395 and3,335,616. Reverse mainshaft gear 128 is in continuous meshingengagement with countershaft gear 112 by means of conventionalintermediate idler gears (not shown). The forwardmost countershaft gear102 is continuously meshed with and driven by input gear 98 for causingrotation of countershaft 90 whenever the input gear is rotatably driven.

Clutch collar 122 carries positive jaw clutch teeth 98b and 114b whichare engageable with clutch teeth 98a and 114a, respectively, to definepositive jaw clutches 98c and 114c, respectively. Clutch collar 124carries positive jaw clutch teeth 116b and 118b which are engageablewith jaw clutch teeth 116a and 118a, respectively, to define positivejaw clutches 116c and 118c, respectively. Jaw clutch collar 126 carriesjaw clutch teeth 120b and 128b which are positively engageable with jawclutch teeth 120a and 128a, respectively, to define positive jawclutches 120c and 128c, respectively.

As is known in the prior art, each of the clutch collars are preferablydirectly or indirectly splined to the mainshaft for rotation therewithand axial movement relative thereto. Other mounting means for the clutchcollars are known in the prior art and are intended to be includedwithin the scope of the present invention. Each of the clutch collars122, 124, and 126 is provided with means for receiving a shift fork orshift yoke 130, 132 and 134, respectively, whereby the clutch collarsare axially moved, one at a time only, from the positions illustrated inFIG. 3 by the actuator 28.

The auxiliary transmission section 96 includes output shaft 22 which ispreferably coaxial with input shaft 72 and mainshaft 100 and issupported for rotation in a transmission housing by means of bearings.The auxiliary section also includes an auxiliary section countershaft 92supported for rotation in the housing by means of bearings. Fixed forrotation with mainshaft 100 is the auxiliary section drive gear 136.Auxiliary section countershaft 92 carries auxiliary section countershaftgears 138 and 140 fixed for rotation therewith. Auxiliary sectioncountershaft gear 138 is constantly meshed with auxiliary section inputgear 136 while auxiliary section countershaft gear 140 is constantlymeshed with output gear 142 which surrounds the output shaft 22. Asynchronized clutch structure 144, of conventional individuallysynchronized jaw clutch design, is utilized to selectively clutchmainshaft 100 and auxiliary drive gear 136 directly to the output shaft22 for a direct drive connection between the mainshaft and output shaftor to clutch output gear 142 to the output shaft 22 for a reductiondrive of output shaft 22 from mainshaft 100 through countershaft 92 asis well known in the prior art. Synchronized clutch structure 144 iscontrolled by shift fork 146 axially moved by actuator 28.

Transmission 14 is of the range type wherein the auxiliary section ratiostep (or steps) is greater than the total ratio coverage of the mainsection ratios appearing in all ranges. Such transmissions are wellknown in the prior art, see U.S. Pat. No. 4,754,665, the disclosure ofwhich is hereby incorporated by reference.

The power synchronizer assembly 30 includes a planetary speed increasinggear set driven by the output shaft 22 independently of the rotationalspeed of the drive engine 16, and selectively actuatable to acceleratethe rotational speed of transmission elements driven by the input shaft72 for purposes of synchronous rotation of jaw clutch members associatedwith the gear ratio to be engaged. Preferably, the power synchronizerassembly 30 will also include means to decelerate the transmissionelements driven by the input shaft. Deceleration of the transmissionelements driven by the input shaft may also be achieved by input shaftand/or engine braking devices which will preferably be controlled bycentral processing unit 50.

The power synchronizer assembly 30 is driven by the vehicle through gear142 which is driven directly or indirectly by output shaft 22 and thusthe power synchronizer is not effective to accelerate the mainsectioncountershaft 90 when the auxiliary section is not engaged.

Details of construction and operation of the power synchronizer assembly30 may be appreciated in greater detail by reference to above-mentionedU.S. Pat. No. 4,614,126.

The shift sequence for a simple shift of transmission 14 in system 12 isillustrated in FIG. 4. Assuming the ECU 50 determines that a shift fromsecond (2nd) to third (3rd) speed is required (i.e. a simple upshift),the ECU will cause fuel controller 34 to defuel (i.e. "dip") the engineregardless of the position of the throttle pedal 32. While the engine isbeing defueled, the disconnect clutch (or master clutch) 24 isdisengaged and shift to mainsection 94 neutral is undertaken.

Upon defueling the engine, declutching the disconnect clutch anddisengaging the mainsection, the power synchronizer is actuated to causethe mainshaft gearing (in this example 3rd speed mainshaft gear 114) torotate at a target or substantially synchronous speed relative tomainshaft 100 as determined by output shaft speed and auxiliary section96 ratio. Output shaft speed is sensed by sensor 44 while the speed ofthe various mainshaft gears is a known multiple of input shaft 72 speedas sensed by sensor 42.

The rail select function can occur at any time after mainsectiondisengagement and mainsection reengagement in the new ratio is timed tooccur as the power synchronizer is bringing the engaged gear towardstarget speed. Of course, for an upshift the power synchronizer isnormally required to retard the speed of the input shaft and associatedgearing.

Upon achieving engagement of the proper mainsection ratio, thedisconnect clutch is reengaged and the engine refueled.

Typically, a simple shift can be accomplished in about 0.70 to 0.80seconds with a disconnect (i.e. torque break) time of about 0.50seconds.

To prevent the engine from accelerating to an undesirably and/ordamagingly high speed upon declutching, and to allow the engine speed todecay during an upshift for smoother reengagement of the master clutchor torque converter disconnect clutch, it is important to determine thatthe throttle dip override device 34 is properly working or, if a faultis sensed, to provide an appropriate fault tolerant mode of operation.

Accordingly to the control system/method of the present invention, seeFIG. 6, just prior to or at the time of commanding actuation of throttledip override device 34, an initial engine speed (E_(o)) is sensed andmemorized. It is then determined if throttle pedal position (THL) isgreater than a reference throttle position equal to about 25% to 30% ofmaximum throttle pedal position. If throttle pedal position does notexceed the reference, then a test for a failure of throttle dip overridedevice actuation is not conducted.

If the fault test is conducted, a timer is set to time a period of time(T_(REF)) equal to about 800 milliseconds at which time a current enginespeed (E_(c)) is sensed and compared to the initial value (E_(o)) todetermine if engine speed has decayed as would be expected if thethrottle dip device is properly operating.

If the engine speed does decay as expected, then the shift sequenceproceeds accordingly. If an engine speed decay does not occur, then athrottle dip actuation fault is declared and the operator may benotified via a fault display. If a shift is required, the shift sequencewill not proceed until the operator manually decreases throttle pedalposition and thus engine fueling, to below a reference value which ispreferably about 25% to 30% of the full throttle position.

Accordingly, it may be seen that a shift control system and method foran automated mechanical transmission system having a throttle dipoverride device for automatic fuel control is provided having throttledip override device actuator fault sensing and fault tolerant logic.

It is understood that the above description of the preferred embodimentis by way of example only and that various modifications, substitutionsand/or rearrangements of the parts are possible without departing fromthe spirit and the scope of the present invention as hereinafterclaimed.

I claim:
 1. A method for controlling shifting an automated mechanicaltransmission system (12) of the type comprising a mechanicaltransmission (14), a fuel controlled engine (16), a nonpositive coupling(10) drivingly interposed the engine and the transmission, an operatorset throttle control device (32), a throttle override device (34)effective to limit the maximum amount of the fuel supplied to the engineto a predetermined amount regardless of the setting of the throttlecontrol device, and a central control unit (50) effective to receiveinput signals indicative of the status of the transmission systemincluding signals indicative of (i) engine speed, and to process same inaccordance with logic rules to issue command output signals to aplurality of system actuators, said method characterized by:sensing fora required shift of said transmission; responding to sensing a requiredshift of said transmission by initiating actuation of said throttleoverride device and sensing and memorizing the initial value of enginespeed (ES_(o)) at the time of initiating actuation of said throttleoverride device; allowing a period of time (T_(REF)) to pass and thensensing the then current engine speed (ES_(c)); and comparing theinitial value of engine speed to the current value of engine speed anddetermining a throttle override device actuation fault if said initialvalue does not exceed said current value by at least a reference value(ES_(o) -ES_(c) ≧REF).
 2. The control method of claim 1 wherein saidreference value (REF) equals zero.
 3. The control method of claim 1wherein said reference value (REF) is greater than zero.
 4. The controlmethod of claims 1, 2 or 3 wherein said input signals also includesignals indicative (ii) of the operator's setting of the throttledevice, said sensing and comparing of engine speeds to determine athrottle override device actuation fault only proceeding if said sensedthrottle setting (THL) exceeds a first throttle position reference(THL_(REF-1)).
 5. The control method of claims 1, 2 or 3 wherein saidinput signals also include signal indicative (ii) of the operator'ssetting of the throttle device and further comprising, if a throttleoverride device actuation fault is determined, preventing transmissionupshifts if sensed throttle position (THL) exceeds a second throttlereference value (THL_(REF-2)).
 6. The control method of claim 4 whereinsaid input signals also include signal indicative (ii) of the operator'ssetting of the throttle device and further comprising, if a throttleoverride device actuation fault is determined, preventing transmissionshifts if sensed throttle position (THL) exceeds a second throttlereference value (THL_(REF-2)).
 7. The method of claim 4 wherein saidfirst throttle reference value (THL_(REF-1)) equals about 20%-30% offull throttle setting.
 8. The method of claim 5 wherein said secondthrottle reference value (THL_(REF-2)) equals about 20% to 30% of fullthrottle.
 9. The method of claim 6 wherein said first throttle referencevalue (THL_(REF-1)) equals about 20%-30% of full throttle setting. 10.The method of claim 9 wherein said second throttle reference value(THL_(REF-2)) equals about 20% to 30% of full throttle.
 11. The methodof claims 1, 2 or 3 wherein said transmission system (14) furtherincludes a power synchronizer assembly (30).
 12. The method of claims 1,2 or 3 wherein said predetermined amount of fuel is about the amount offuel required to maintain said engine at about an idle speed settingthereof.
 13. The method of claims 1, 2 or 3 additionally comprisingnotifying the operator of a fault upon determining the existence of athrottle override device actuation fault.
 14. The method of claims 1, 2or 3 wherein said period of time is in the range of 500 to 1000milliseconds.
 15. A control system for controlling shifting an automatedmechanical transmission system (12) of the type comprising a mechanicaltransmission (14), a fuel controlled engine (16), a nonpositive coupling(10) drivingly interposed the engine and the transmission, an operatorset throttle control device (32), a throttle override device (34)effective to limit the maximum amount of the fuel supplied to the engineto a predetermined amount regardless of the setting of the throttlecontrol device, and a central control unit (50) effective to receiveinput signals indicative of the status of the transmission systemincluding signals indicative of (i) engine speed, and to process same inaccordance with logic rules to issue command output signals to aplurality of system actuators, said system characterized by said logicrules including rules:for sensing for a required shift of saidtransmission; for responding to sensing a required shift of saidtransmission for by (i) initiating actuation of said throttle overridedevice and (ii) sensing and memorizing the initial value of engine speed(ES_(o)) at the time of initiating actuation of said throttle overridedevice; for allowing a period of time (T_(REF)) to pass and then sensingthe then current engine speed (ES_(c)); and for (i) comparing theinitial value of engine speed to the current value of engine speed and(ii) determining a throttle override device actuation fault if saidinitial value does not exceed said current value by at least a referencevalue (ES_(o) -ES_(c) ≧REF).
 16. The control system of claim 15 whereinsaid reference value (REF) equals zero.
 17. The control system of claim15 wherein said reference value (REF) is greater than zero.
 18. Thecontrol system of claims 15, 16 or 17 wherein said input signals alsoinclude signals indicative (ii) of the operator's setting of thethrottle device, said sensing and comparing of engine speeds todetermine a throttle override device actuation fault only proceeding ifsaid sensed throttle setting (THL) exceeds a first throttle positionreference (THL_(REF-1)).
 19. The control system of claims 15, 16 or 17wherein said input signals also include signal indicative (ii) of theoperator's setting of the throttle device and further comprising, if athrottle override device actuation fault is determined, preventingtransmission upshifts if sensed throttle position (THL) exceeds a secondthrottle reference value (THL_(REF-2)).
 20. The control system of claim18 wherein said input signals also include signal indicative (ii) of theoperator's setting of the throttle device and further comprising, if athrottle override device actuation fault is determined, preventingtransmission shifts if sensed throttle position (THL) exceeds a secondthrottle reference value (THL_(REF-2)).
 21. The control system of claim18 wherein said first throttle reference value (THL_(REF-1)) equalsabout 20%-30% of full throttle setting.
 22. The control system of claim19 wherein said second throttle reference value (THL_(REF-2)) equalsabout 20% to 30% of full throttle.
 23. The control system of claims 15,16 or 17 wherein said predetermined amount of fuel is about the amountof fuel required to maintain said engine at an idle speed settingthereof.
 24. The control system of claims 15, 16 or 17 additionallycomprising rules for notifying the operator of a fault upon determiningthe existence of a throttle override device actuation fault.
 25. Thecontrol system of claims 15, 16 or 17 wherein said period of time is inthe range of 500 to 1000 milliseconds.